Ranging receivers generally are designed as superheterodyne radios with one or more Intermediate Frequency (IF) amplifiers. To suppress adjacent channel interference, these IF amplifiers are provided with selectivity accomplished with bandpass filters. Bandpass filters are conventionally characterized by low and high cut-off frequencies, fL and fH, respectively, defining the bandpass half power response limits. The difference between fH and fL is referred to as the filter bandwidth, B. The geometric mean frequency
            f      L        ⁢          f      H      constitutes the filter's center frequency, fC . The ratio of the center frequency to filter bandwidth,
            f      C        B    ,is often referred to as the filter Q-value. When graphed on a linear frequency scale, there will be evidenced non-linearity in the filter phase response. This gives rise to a non-uniform group delay across the response band which affects the receiver's transient response. For a given bandwidth, Q decreases (increases) as fC decreases (increases). Phase response non-linearity increases as the value of Q decreases due to the increasing departure of fC from the arithmetic mean frequency
      f    M    =                              f          L                +                  f          H                    2        .  